The proposed workshop will be organized in March 2005 to (1) reach consensus on definitions of the stages of the caries process that can portray the concept of demineralization at the precavitated stage; (2) define the stages of the caries process and indicators of caries activity that should be measured in clinical research; (3) develop operational definitions and structure for a Standard Operating Manual for the clinical detection and assessment of dental caries; and (4) define clinically relevant validation methods and a research agenda for the newly developed clinical detection visual system. This workshop will be the fifth workshop organized by an ad hoc group of caries researchers from the USA and Europe. The group, referred to as the ICDAS committee, includes a representative from NTDCC (Dr. Robert Selwitz). The ICDAS committee includes the following members: David Banting (Canada), Hafstein Eggerston (USA and Iceland), Amid Ismail (USA), Kim Ekstrand (Denmark), Christopher Longbottom (Scotland), Nigel Pitts (Scotland), Elmar Reich (Germany), David Ricketts (Scotland), Robert Selwitz (USA, NIDCR), Woosung Sohn (USA), Gail Topping (Scotland), Andrea Ferreira Zandona (USA), Domenick Zero (USA). The ICDAS committee has developed clinical detection criteria that incorporate the current state of science in understanding the caries process. The criteria system has been used in research projects in the USA and Europe (Appendix A) were found to have very good to excellent reliability. The proposed workshop will build on the foundation developed by ICDAS and seek wider consensus on caries detection criteria from leaders in the field of research in clinical cariology. The future progress of clinical research will depend on developing a new system of measurement. The ICDAS mission is to achieve this goal. This workshop will achieve this goal and build the foundation for changes in the way dental caries is measured and managed (using remineralization as well as surgical care). Finding of the workshop will be used in a second workshop, to be organized by Dr. George Stookey, which will focus on the design of caries clinical trials and new diagnostic technology.